The need to provide a vacuum environment for operation of electronic components and devices is well documented in the art. For example, vacuum tube devices operate, of necessity, in a vacuum environment which is realized by employing an evacuated and sealed glass envelope in which the active device is disposed.
Presently, research activity is focusing on methods to implement vacuum device technology employing microelectronic structures. These structures, in many instances, are comprised of arrays of individual devices disposed on a suitable supporting substrate. One particular application of a microelectronic vacuum device structure is as a flat image display.
A number of undesirable features of present technology make the implementation of flat displays employing microelectronic vacuum devices difficult to realize. Prior art methods of effecting a seal about the encapsulating structure, which may be a display faceplate, to the substrate on which the microelectronic vacuum devices are disposed is generally a process which requires high temperatures. During cool-down objectionably large bulk stresses are created in the structure which induce failure during device operation.
Further, prior art methods of providing an evacuated region for device operation result in significant deformation of the substrate as a result of the large differential pressure between the evacuated region and the external environment. One prior art method employed to overcome the objectionable deformation of the substrate is described by Brodie (U.S. Pat. No. 4,923,421) wherein a method for providing polyimide spacers in a field emission panel display is described. This prior art technique requires incorporation of an array of spacers as part of the overall structure which introduces an objectionable complexity to device fabrication.
Additionally, prior art methods, including those described above and others require that display device assemblies in particular and microelectronic vacuum device assemblies in general be assembled within an evacuated environment.
In prior art applications the vacuum requirements imposed on the device structure precludes the possibility that many known sealing materials may be used since these sealing materials are known to out-gas when disposed in a vacuum environment on the order of 1.times.10.sup.-5 Torr. or less.
Accordingly there exists a need for an improved vacuum enclosure and method for providing an improved vacuum enclosure which overcomes at least some of the shortcomings of the prior art.